240 



concludes that the larger cells represent the head end of the embryo 

 and the small ones the tail end. 



These facts seem to leave no doubt as to the frequent existence 

 of an area of special growth which determines the position of the forth- 

 coming blastopore and consequently the posterior end of the embryo. 

 As stated in an earlier paragraph the primary area of cellular 

 activity is at or near the upper pole and it determines the position of 



the future head end of the embryo. 

 The heavily dotted portion in the 

 center of the accompanying dia- 

 gram (Fig. 47) indicates in a 

 general way the area which deter- 

 mines the position of the head of 

 the embryo. Its median sagittal 

 plane may fall in any one of an 

 indefinite number of meridians 

 (a, 6, c, d^ e, f etc.). On the 

 appearance of the secondary area 

 to which reference has already 

 been made, it is possible to locate 

 definitely the position of the 

 forthcoming blastopore and con- 

 sequently the median plane of the future embryo. A line {x) passing 

 through the centers of the two areas coincides with the median plane 

 of the future embryo. 



Nachdruck verboten. 



Zur Wirkung- Ton Säure auf die roten Blutkörperchen 

 der Amphibien. 



(Vorläufige Mitteilung.) 

 Von Friedrich Meves. 



Kneuttinger ^) hat im Jahre 1865 beschrieben, daß die roten 

 Blutkörperchen des Frosches bei der Einwirkung von Säure sich unter 

 Erhaltung der elliptischen Scheibenform plötzlich wie mit einem Ruck 

 nach allen Richtungen erweitern. 



„Setzt man 7,2-proz. Essigsäure zu einem Präparate, so bekommen 

 die Blutkörperchen kleine Einbiegungen, Einkerbungen, und es er- 



1) G. Kneuttinger, Zur Histologie des Blutes. Würzburg 1865. 



